I bought one from LPS a while ago for around $4.20 to $4.50 If I remember correctly.
Klaus makes up hardwood dowel dummies with nails through the center for 34MM long 123 size, 17MM long 1/2 123 size and, and 50.5 mm long aa size.
Klaus' dummies aren't a pretty as the SF dummy but they work. He doesn't make them for sale but has been persuaded to do so as an inducement to trade.
I have used the 17 MM size to combine 3@ Alkaline AA's plus a CR123 on each side of a serial - parallel DB8AA to drive a 9.0 V 1.1 A W/A bulb.
I've also drilled a 3/4" hole in the center of two 58 mm long 1 1/4" dowel to use one of the 17mm dummies along with a 43mm long rechargeable 4/5 A cell as a charging adapter fixture for this odd cell. The combined length of 60 MM compares to the 61 mm of a D cell.
Similarly, I'm thinking of drilling some 15/16" holes in the center of a few of these dowel sections to make a charging adapter fixture for 43mm long 3000 mAh sub C cells.