Several quick things.
First, I ordered mine from here
and got them in a few days.
Second, I went ahead and had new tires put on last Friday and I forgot to take the valve stems to the shop.
Well, they went ahead and worked me back in Saturday (being able to leave the bike for a few hours helped) and they switched them out for me - no charge (esp. since they overcharged me a bit on the tires - I still won price-wise). They have a tool that will do it.
Third, a few years ago I had one of those dreadful rubber angled valve stems give way on the freeway. The town I stopped in didn't have any electricity (the town's co-op transformer was blown and some of the locals had taken a truck to go get another one).* The shop managed to break the bead by hand (I think) and slip a new rubber valve stem in (best $15 I spent on that trip).
So yes, it can be done - a small pair of clamps might help - I don't know. I hope this helps.
* Whitehall, MT
I’m not afraid to go fast – it’s the crashing and burning that scares me.
Actually, I'm too cheap to go too fast. Have you seen the price of gas lately?
It's SO time for another long road trip!!!