SunRace offer a very inexpensive 5 or 6 sp freewheel. 3 of 4 purchased over the years were OK, the other had an issue threading on the hub, i set it aside without determining if it is really a reject.
IRD offer freewheels, $69.95 on their website.
My experience when buying used - is to buy from someone I know, or a bike store or co-op that sells used bikes and has a service reputation. edit after seeing other replies = yes on new chain. I generally use an 8sp SRAM or KMC.
Last edited by Wildwood; 03-30-20 at 01:58 PM.