Information for Burnt_Retinas' Magic resistor
6 X NiMH in a modified Electrolumens 6 AA to D carrier (or possibly the new EL 3>d would be good with out mods) is highly recommend.
Note, there is a large TO-220 FET buried in the hotlips.
U1 = TL431. It's a voltage reference. Available in either SMT or through hole (to-92 type package).
U2 = LM358 op=amp. Also available SMT (SO-8) and through hole (SIP) package.
Q1 = The FET. It's an IRF3703 = overkill and perhaps hard to get. Many others will substitute, but they may not have such low on-resistance.
Instructions on How to remove MR/Hotlips combo and Current adjustment instructions.(Very Large pic make sure you take of "screen fit" or you wont be able to read it)