Here are some more, but more expensive.
But since they don't make them any more I think they are collector items.

I think you can still get the 8 foot from GE, but not the four foot.
I would like to have two, but I think they are a little high on price and I would bet that there a still a few laying around in the back shelf of a stock room somewhere as they are not all that old.
The price has now been reduced and the one above never got a bid @ $26.
Must not be a hot seller.
http://www.ebay.com/itm/GE-Power-Groove-Lamp-Bulb-F48PR17-CW-NOS-VINTAGE-ANTIQUE-LIGHTING-F48pg17-CW/111290939893?_trksid=p2047675.c100010.m2109&_trkparms=aid%3D555012%26algo%3DPW.MBE%26ao%3D1%26asc%3D20131231084308%26meid%3D5262562008085619539%26pid%3D100010%26prg%3D20131231084308%26rk%3D0%26rkt%3D24%26sd%3D121286141379Here are seven NOS F72PG17CW as a set.
I think you can still buy the 8 foot PG new from GE last time I checked.
But I can't find any F72PG17 CW listed.
Is this a rare bulb?
http://www.ebay.com/itm/GE-Power-Groove-Lamp-Bulb-F72PG17-CW-NOS-VINTAGE-ANTIQUE-LIGHTING-F72PG17-CW-7PC/201037635993?_trksid=p2047675.c100011.m1850&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20466%26meid%3D5320995965760562142%26pid%3D100011%26prg%3D9138%26rk%3D1%26rkt%3D10%26sd%3D121286141379