you can get a G&P G90 from:
http://www.lighthound.com/index.asp?PageAction=VIEWPROD&ProdID=1203
you could try a pathfinder P90 (which is similar, uses about 1.33amp as apposed to 1.2amp) here
http://www.qualitychinagoods.com/bulb-ultrafire-wf502b-p-403.html
this bulb might also work well: (havn't heard if anyone here has tried it out yet)...
http://www.qualitychinagoods.com/bulb-wf501b-p-521.html
there's some ebay sources for them as well:
http://cgi.ebay.com/G-P-G90-XENON-Lamp-Assembly-SureFire-9P-D3-C3-Z3-GP029_W0QQitemZ270069697757QQihZ017QQcategoryZ106988QQtcZphotoQQcmdZViewItem
I believe that fifthunit also carries them but his site is down at the moment
http://contents.fifthunit.com/html/products.5th/category.0.html
might be woth holding out to see his price, he is usually really cheap.
[edit in]
you should also consider the LumensFactory SR-9 and ES-9 as good candidates for a 2xRCR123config.
You could also run a D26 from Wolf-Eyes, which is also a darn good lamp.
http://www.pts-flashlights.com/products/product.aspx?pid=1-25-26-46-6091
I believe this Pila lamps will also fit:
http://www.jsburlysflashlights.com/cgi-bin/ccp51//cp-app.cgi?usr=51I1089811&rnd=1291811&rrc=N&affl=&cip=70.59.197.221&act=&aff=&pg=prod&ref=Pila_GL3_9V_lamp&cat=pila_lamps&catstr=HOMEila_lightsila_lamps
oh yea.. you can also use a Surefire P90.. doesn't make since to start spending more on 1 lamp assembly than the flashlight costs to begin with? or does it? lol. (my P91 costs more than the ultrafire I use it in, lol)....
I say buy one of each, then you'll know for sure!!!
hehe... ok... so seriously- I think I would go with the D26 if you wanted one of the brighter options of the bunch with a reasonable runtime, (probably going to be around 20 minuts)... or the ES-9 from Lumensfactory if you want it to run nice and long.