See if you credit union offer secured loans.
Or failing that, if one of the banks will.
Rate won't be as low as a mortgage, but by giving them a legal charge over property it'll be less than a standard loan.
You will have to pay the legal costs, but shouldn't be much when being done as part of purchase.
Even though you're not looking for much, a bank can only lend what you can afford to repay, so they will have to assess affordability in a similar way that they would with a mortgage.