In case anyone here is looking-- Menards has the HTC 1000 mobile base for $35 after a $5 rebate.
It has a "PortAMate" brand name on it, so at first I thought it was some Menards Taiwanese special, but then saw the copyright: HTC Products, Inc. Made in USA.
This is the first mobile base I've had, so can't compare it to others, but it was quick to assemble and seems well made. Plenty sturdy enough for moving my planer over the rough garage floor.
BTW, Menards is only in Minnesota and Wisconsin, I think.