I used to carry Mag Solitaires on my keychain for years, and also own a Dorcy 1-AAA LED. While the Dorcy is superior in that its "bulb" can't burn out and it puts out more light for a longer time, I don't feel that it is built nearly as well as a Solitaire, and I don't think it would last nearly as long if tossed in a pocket with keys everyday. I'd recommend a CMG Sonic or ARC AAA for everyday keychain carry as being superior (build quality) to the Solitaire and the Dorcy.
That being said, I'm not aware of any 1.5V bi-pin bulbs that are superior to the ones Mag sells. If you want to keep using the Solitaire, I'd suggest finding the cheapest supplier and buy a dozen bulbs at a time, and make sure you keep fresh batteries in it. I found the Solitaire to be best with a fresh bulb, fresh battery, and freshly cleaned contacts/connections (but even then, it still can't compare to my ARC AAA).
-Keith