Purchased item damaged during shipping

I purchased an electronics item (a subwoofer) that was damaged during shipping (USPS). It still works but one of the feet broke off. In addition to it no longer being what I purchased, the part is not available from the manufacturer or online. It is a down firing sub so I would need to replace the foot with something for it to work as intended.

It's quite a bummer because the item is relatively rare and I got it for a good price. I let the seller know and he was responsive. Said he'd check with to see if the feet are available, but I reached out on my own and see that they are not.

Anyway, aside from asking for a refund, is there another possibility here to make things right? It also is quite heavy so while I can ship it back, it would be a bit of a hassle and I am not sure who pays and how? I also don't want to be underhanded, but is it reasonable and possible to work out a comprise where I can some of my money back? Or does offerup offer a possible remedy?