I hear Honduras has some left.
Honduran rosewood (Dalbergia stevensonii) is mostly from Belize, formerly British Honduras which is presumably the source of the Honduran designation. All Dalbergia species are subject to the CITES restrictions now, so one has to have permits to export it. Additionally, the government of Belize has instituted a logging ban until such a point that they believe it can be sustainably logged again. I think most of what gets out nowadays is old salvage.
But, there's a bunch of stuff already in the US. It's actually not too difficult to Google some sources, and you can find the wood for sale on eBay, Etsy, and Instagram. Search using both "Honduran rosewood" and "Honduras rosewood". Right now there's a listing on eBay from a reliable seller I've bought from for a turning block that has sapwood on it, and priced for less than $11. I see a block from a different seller for just over $5. So it's out there if you look for it like Stacy said.
If you're looking specifically for the burl, that stuff is a little rarer and more expensive. HRB is my favorite wood, but I've been able to save a decent amount of it, probably more than I'll ever be able to use LOL. Below is a knife I made with some that I'd been saving for a few years, and I was really jazzed how it turned out. The figure and movement in the wood is amazingly beautiful.
One thing you might consider if you can't find a piece that you really like, you might consider other striking woods like bocote. Both desert ironwood and cocobolo will make very striking knife handles when you have both heartwood and sapwood showing.