How about companies release "special" editions of products for a slightly higher price and donating the difference to a fund for RISC OS related projects. This could extend to not only ROOL but other projects that have overheads but no income to cover them e.g. Netsurf, open source projects, updating popular freeware applications.
Products like printers, monitors, consumables etc could be sold with say a 5% margin added that is donated to a fund. All that would be required is someone to manage the fund and people to apply for money from it.
Given the size of the market any new ways of bringing in funding must be of benefit.