Tshadow tried stationery bike and found it caused great flares.

Here's something to try:

Lie down behind the stationery bike. Place a mat on the ground and something for your neck if you desire stabilization.
Place your feet in the pedals (need those clip things) and begin. This allows your lower body to exercise while the upper body remains immobilized. You just have to get the correct resistance adjustment before you lie down or have someone there to set it for you.

I learned this also in PeterEdgelow's PT as the treadmill walk flared me up.

YOu could also try a recumbent bike with a board placed behind you to support your body all the way up to your head. You get the board at the gym or club where you use the bike. It's light weight and covered with the same material as their exercise machines.

Other things to try are machines where your feet dont' leave the ground. Like Ellypticals, X-Country machines. I don't use any arms w/any machines-I find a way to keep my arms immobilized as using them causes flare.

However w/vascular now I find ellypticals too vigorous. The swelling begins after just a few minutes. And I saw shaking and discoloration too.