If 12u wont fit, you're not setup to build something, and dont mind your gear being in a loose stack then something like this might do the trick

https://www.amazon.com/MaxWorks-80854-Polypropylene-Dolly-200-lb-Capacity/dp/B07C72GWLT/

I use this: https://smile.amazon.com/dp/B07C72GWLT/?coliid=I2Q0YZUNYF2BC1&colid=1VDVAWYC6SAQJ&psc=1&ref_=lv_ov_lig_dp_it