So I have 2 commercially purchased rolling bases under bandsaws in my shop.
I have an HTC HTC2000 base under my Grizzly saw and a Grizzly Bear Crawl "Cub" base under "1947", a Delta bandsaw. The "Cub" appears to be the same parts as their other bases with shorter arms - but I could be wrong.
Both bases have 2 fixed wheels and 2 swivel wheels but the lock mechanisms have different approaches.
The HTC has fixed pads and you push a lever to the swivel wheel lift up, landing the machine on the pads to lock it into position. The Grizzly has 2 pads that you push a lever to push them to the ground to lock the position.
The Grizzly is a heavier duty base (IMHO) and they make something that would work for a Unisaw with an extended table if that's necessary in your case. You just need to measure the base of your saw and see what they have that fits.
https://www.grizzly.com/mobile-bases
I built a custom cabinet under my Jet contractor saw with drawers and double lock casters. I had the rear set of casters tack welded into position so they no longer rotate but still lock the wheel. The first attempt had non-rotating / non-locking casters on the rear and I got some "slide" at times based on the loading of the front casters on my wavy garage floor.
Cheers
Jim