Some of the parts listed at http://otgw.tclcode.com/schematic.html#partlist are no longer available at Conrad. I have an updated list for some of the common parts (the resistors), yet for some parts I am not able to find it next-gen alternative.
The transistor doesn't really have to be a specific type. Pretty much any NPN transistor will do. If you still have some in your box of components, they will probably work. The only requirement is that they can handle a collector-emittor voltage of 30V. If you have to order one from conrad, just pick the cheapest TO92 NPN transistor. At the moment that is 1262957 - 89.
Unfortunately the voltage regulator is less clear. Without actually testing them it's hard to be sure if they are still able to produce a steady 5V output when the input voltage is around 25V. Experience has shown that not all TO220 7805 can do that equally well. The ones in TO92 package usually can't. Conrad currently seems to have 2 reasonable candidates: 175030 - 89 and 179205 - 89. The data sheets of both devices suggest that they should work correctly between 8V and 25V. Given their price I would just order both and check on the bench which input voltage range they can handle. If you do, it would help others if you report back your findings.
I bought the 175030 voltage regulator and the 1262960 NPN transistor from Conrad for my second OTGW. Soldered them onto the pcb (together with all other components), programmed the PIC, plugged it in and it worked immediately. Has been working ever since, without glitches.
@hvxl: maybe you could put a part in where the bigger transistor and the RECOM-replacement of the 7805 is mentioned? That way people know up front about the upgraded availabilities regarding powering other devices. I'm also happy to supply the text if you need me to.
Damn! I went and splurged on a more expensive transistor (well, only €0.16 more) - part number 563804 - 89.
I also installed the RECOM R-78E5.0-0.5 DC/DC-converter, print 24 V/DC 5 V/DC 500 mA (part 157954 - 89) and used the EI 30/15,5 printtransformator VB 2 VA Primair: Secundair: 2 VA VB 2,0/1/15 Block (part number 710564 - 89) transformer so I could run an Adafruit Huzzah ESP8266 directly connected without the need for additional power supplies or circuitry. All measurements were nicely in spec and has been solid as a rock since I installed it a month ago.