I think they're a plastic reyjkavik reproduction but I cannot find the seller. All the sets I found have a different pawn, but I'm almost sure it is a Reyjkavik.
Chess Set used in "The Two Chess Hustlers Who Swindled Hikaru"

Look up Shelby Lohrman here on chess.com he runs the outfit and if I'm not mistaken last I heard he was down to around 50 sets. It does look like it may have been loosely based on the Reykjavik set though.

Following the link for the clearance butters provided by @Pawnerai, the text and youtube preview image are leading me to believe that these pieces are using the new and improved weighting system. Is that actually the case or am I just misunderstanding?! I *thought* the new system was introduced with the new appliance white set we've been buying from here:
https://amchesseq.com/collections/premium-chess-pieces/products/bobby-fischer-ultimate-chess-pieces-with-new-and-improved-weighting-system?variant=32118482993210
Thanks as always!

@lotsoblots
The v2 yellow "Butters" Ultimates are only available with the "regular" weighting system. Linked in Post #6.
The v3 ivory Ultimates are only available with the "new and improved" weighting system. Released at the end of 2020. Linked in Post #9.
I just glanced at the product descriptions of the two sets on the amchesseq site. The language used is not very clear. And I can see why you were confused.

Following the link for the clearance butters provided by @Pawnerai, the text and youtube preview image are leading me to believe that these pieces are using the new and improved weighting system. Is that actually the case or am I just misunderstanding?! I *thought* the new system was introduced with the new appliance white set we've been buying from here:
https://amchesseq.com/collections/premium-chess-pieces/products/bobby-fischer-ultimate-chess-pieces-with-new-and-improved-weighting-system?variant=32118482993210
Thanks as always!
LotsoBlots,
I went and updated the info on the weighting system for the V.3 pieces. Changed the wording from "Premier" to "Exclusive" and put a better description of what we did with them.
Hope that helps!
Shelby Lohrman
American Chess Equipment

Got to say that the butter Ultimates looked much more yellow in that video than they do in real life. Still, I'm glad to have my own set of butters.

I was looking the same piece set, but trying to purchase it from Europe. Could somebody recommend a shop or website that provide it to EU? Best regards!

Have you checked Spain's Amazon? Here in the US, Amazon sells the v3 Ivory version of the Ultimates with the new and improved weighting system. No Butter yellow unfortunately.
https://www.amazon.com/dp/B07C2HPMQ5
"
Hi @Pawneral, thanks for your suggestion. Yes, I checked Amazon but is not available to send it to Spain.
Looking on eBay (https://www.ebay.es/itm/303557370378) I found one V2 set (I like the butter color) but I'm not sure if it's a clone or not, anyway, It's priced on 60$ aprox including taxes, that maybe it's too pricey but I'm thinking on buy it at all because probably I regret myself in the future when no more butter sets exists.
I was wondering what chess pieces were being used when Hikaru played John Brooks in Monroe Street Midway in Detroit. Are they weighted? They look really nice and I'd like a set. Any info would be great.
You can see it in the youtube vid here: https://www.youtube.com/watch?v=FJ4qlNWWQEI (3:02)