Try and find somewhere locally that sells rubber. They'll have a variety of rubber edgings and one of them is bound to be what you want. It will probably only come in black, but there is always Vinyl Dye to change it It will be cheap though!
eg, this is one of my local rubber places Para Rubber
Go down to your local computer store, and pay them $1.00 for a junk power supply. Rip the grommet off the dead power supply and put it on your new one.
Since you have such a tight radius to trun, try heating it up with a hair dryer to get it to bend better. If you have a heatgun, that would work better.
I bought a box of grommets from the local autoparts store. They sell them in the electrical isle (look for the red clam shell under the brand name "Help!")... if none of those suit your needs check the tune-up/oil change isle and look for PCV (Positive Crankcase Ventilation) grommets.
PVC valves on some older Chrysler V8s are about 1-1/2" in diameter. Some make/models are larger, some are smaller but you should be able to find exactly what you're looking for.