It's a necked up .307 Winchester case so you can get those as well and convert them (the head stamp will be wrong though). A quick search also shows that .444 Marlin brass might also work but if it does, it'd be more work. I know I've seen .307 Win around from time to time but I can't remember the last time I saw .356 Win brass or loaded ammo anywhere.
It looks like Winchester does still make ammo for it in their Super-X line with 200gr bullets but it'll be pricey. What I found on Google was in the US and ran US$60/20rnds. Likely a special-order situation from most gun stores.
Various reports online as well of converted .308 Win brass working in most rifles; specifically the Marlin's. .356 Win is a necked up .307 Win which is just a .308 Win with a small rim on it so the case will be mostly the right dimensions; just a question of if the extractor in the specific rifle you're looking at will grab the rimless .308 Win case heads.
If it's a good price, and you reload, I'd go for it.