The Quinn family confirmed last night there had been "multiple offers of assistance" and said they were "exploring all options", including offers of financial support.
They are now representing themselves in a host of legal actions with the IBRC (formerly Anglo) after parting ways with their legal team.
The family are suing the bank for alleged fraud, claiming more than €2bn worth of loans given to them by the bank are unlawful because they were used to prop up Anglo's collapsing share price.
Bankrupt Mr Quinn is himself a defendant in the legal action brought by his family after being joined in the case by the IBRC.
The Quinn family's bank accounts have been frozen b the courts and receivers have been appointed over their global assets -- leaving them with no control over their financial affairs or access to millions the bank believes they have stashed away.
The family, who are allowed to apply to the courts to release money for legal representation, have denied they are sitting on a "pot of gold".
In a statement to the Irish Independent, the Quinn family said they were "absolutely determined" to proceed to trial with the main case against Anglo -- even if this means they have to represent themselves.
Now, donors have emerged to ensure the Quinn family's case against the IBRC goes ahead.
The identity of the alleged €500,000 donor is not known.
But the existence of the donor was revealed at a recent committee meeting of Concerned Irish Citizens (CIC), a local lobby group formed to support the Quinn family. The group, which met last night to finalise plans for Sunday's rally, has claimed that the group has been inundated with offers of financial support to help fund legal action against the IBRC.
CIC has moved to quell suggestions that people attending Sunday's second rally in Ballyconnell will be charged to attend or that buckets will be passed around at the event to raise money.
"A lot of people have come forward to offer their financial support, said CIC's Patricia Gilheany. "They feel very strongly about the case."
Today, the names of prominent speakers from the business and community world who will address the rally will be revealed.
Several members of the Quinn family have been invited to speak at the rally and have accepted the offer to do so.
The Quinn family's woes deepened yesterday when Paul Appleby, the outgoing Director of Corporate Enforcement, said the administrators of Quinn Insurance Limited (QIL) could go to the High Court to make former directors of the firm personally responsible for the company's debts.
Mr Appleby said that the court could declare that the former directors were personally liable.
Taxpayers could be left footing a bill of up to €1.6bn following the takeover of Quinn Insurance.
The bill will be paid by taxpayers through an annual 2pc levy on all general insurance policies.
The developments came as IBRC tightened its grip on a key Quinn property asset.
Lyndhurst, a British Virgin Islands company, yesterday failed in a High Court bid in Belfast to challenge a ruling, which returned control of the debt associated with a €60m shopping centre in Kiev to the IBRC.
Last May, the IBRC (Anglo) successfully overturned the transfer of $45m (€34m) debt associated with the €60m Ukrania Shopping Centre in Kiev from a Quinn-owned company to Lyndhurst.
Yesterday, Judge McCloskey ruled that there had been further assignments of the underlying debt from Lyndhurst to Ukrainian companies Zenith and Elegant Invest -- transfers that allegedly took place in December 2011 but had not been disclosed to the High Court.
The IBRC argued that the new transfers amounted to further attempts to place the multi-million-euro assets beyond its reach.
"With each passing phase of this litigation, the correctness of this finding is vindicated and fortified," said Judge McCloskey.
The ruling bolsters the IBRC's efforts to secure control of the shopping centre, one of three key assets in the Quinn family's international property group.