Probably the most economic choice right now is a
KBParadise V60 with Matias linear switches (not SKCM, but still close enough), or maybe go further by swapping them out with other SKCM/SKCL, since I think NOS SKCL Yellow is still available on Taobao and getting more common SKCM/SKCL switches isn't too expansive/hard and you can just linearize them. Or maybe a
XD60 or
AEK64 built for more flexibility, though it is more troublesome this way.
Alternatively, you can go for the more common vintage chassis like AT101 or Focus FK-2001, though finding one in good condition and reasonably priced is pretty hard nowadays, since price fluctuates a lot, you'll need to pay close attention on mechmarket or eBay.