Have you called around to your local kart shops? New Burris 33A tires don't seem to be too hard to get but aren't always available same day but usually with in a week or two. Used tires, sometimes mounted on wheels, are readily available on FB marketplace. New wheels are starting to come back around too. Throughout the past 12 months I've not really had difficulty sourcing brand new wheels (bought 20+ sets of VanK's) or Burris 33A tires. I had to pay prime prices a couple of times to get what I wanted but I could always find it. I don't have a secret way of finding these items. I simply start calling around to shops and asking at the track. You can try Palmetto Speed Shop, JC Specialty, Welch's performance, Carlson's, EC Tillotson, PMC (Slack), Uncle Franks, TS Racing, TRJ Karting, etc. I'd start local and go from there.