I would either place an ad in your local Craigslist or post the tires on Fleabay. I've used both sites recently - one for selling and the other for buying.
I just sold four 18" Pirelli A/S tires w/5k miles for $300 that were removed off my wife's Audi Allroad since we did a 20" upgrade shortly after leasing the car (and then eventually buying it).
And would you believe - I had to recently BUY (used) RFTs!!! Yes, and here's the short story (apologize for the thread-jack, but maybe my experiences will give you insight on what to do next...)
With my '17 Q60 AWD, I've been running the stock RFTs until I "burn them down". My plan is to get some forged or flow-formed wheels in the Spring '20. Well, I was getting there, and then I picked up a nail in the left rear a couple weeks back. I removed the wheel, took it to Discount Tire for a flat repair.
Unfortunately, this tire is snake-bit. It already had two patches, and while the nail was in the middle section of the tire, it also picked a smaller nail in the shoulder, so no repair, and the tire was scrapped. I opted to go searching an buy a used tire(s) on Fleabay. I found two RFTs with 8/32" thread depth for $269. While this will p**s off the members here, I wasn't left with many options that didn't either buy new RFTs @ $500+ each, or replace all the 19" tires on stock Red Sport wheels, or move up my plan, which could be up to $5k with the forged wheel option.
So now I have 5/32" RFTs on the front axle, and 8/32" RFTs on the back axle.
2017 Q60 Red Sport AWD Iridium Blue / Monaco Red / Premium Plus Package 3.0t Sport / Infiniti Sport Mats / FI Full Catted DPs & CBE / Stoptech Trophy BBK FR & RR w/SS-Braided Brake Lines / Infiniti HE / Infiniti Intakes / AMS HPFP / Ecutek Tune / BMS Pedal Tuner / Infiniti Radiant Sport Grille / EMM Tuning CF Foglight Finishers / CF Duckbill RR Spoiler / Mishimoto OCC / Stillen Rear Stab Future: AMS LPFP / AMS CF DS / Z1 LSD / Vorsteiner 20" VFF 112s (Staggered) / Michelin Pilot 4Ss