Congrats on the DPAs!
Cheapest/smallest thing for lowpro work is the Denecke PS/2 with a stereo miniplug out. That means you're relying on the pre of your portable recorder, though.
The LB is not very stealthable (although it is small), but it sounds good with the mics. For full-on lowpro work I'd say to wait for the tinybox and get the PS/2 in the meantime. To put it in perspective, I'd run 4021s in mobile fashion with the LB in a bag, but at a show where I was stealthing without guilt due to venue not allowing stands. Also, the LB knobs are pretty easy to move, so you need to tape them down if you want to do that.
That used Oade 248 in the YS will make amazing recordings with the 4022s, and it's at least small enough to carry in a bag (not to mention internal battery powered). I guess it's not much cheaper than the Lunatec pres though, but it is a little....
Your other option is an all-in-one deck like the Marantz 661. That is also a fine option. One of my buddies here runs his 4021s straight into a 660, which I've borrowed and run a few times, and that combo sounds quite nice (it's an Oade mod 660).