There's a few head/engine guys on this forum that may have some for sale.

Summit and Jeg's both still have them listed on their site.

There's a used set on eBay right now:

https://www.ebay.com/i/123437810980?chn=ps

Otherwise I'd check out the For Sale - Small Block engine section on Moparts, Racingjunk.com, and Craigslist.

Whether you buy new or used, I'd have them checked out by someone who knows what they are doing.