Honestly I think your best bet might be to get one made custom (Acopian?). If I remember correctly the specs for it are in the manual and it didn't seem very strange/non-standard.
I parted out a GL2200 and sold the internal power supply on eBay, it went for about $100 earlier this year. If I remember right is +/-15 and +5, and the voltages are marked on the back of the console and in the manual. The GL2200 has the XLR connector for an external backup power supply which improves the noise floor a little. The Allen and Heath RPS9 is the power supply that will work for that, which is about $200 and a lot more serviceable than the internal one.
Thanks guys I'm using the GL2200 in a studio setup atm so it would be nice to have the external PSU so I can have my controlroom as silent as possible. Not that the fan of the internal PSU is that bothering but if I can get my hands on the ext. one it would be cool
If anyone is still having PSU issues please note I had the same problem, a failed internal PSU and no externals available except a real pricey one at Β£700
I made contact with Tim Scott at Dantech a firm in the UK that makes switch mode PSUs and they made me a custom built 19" rack mountable 2U, black powder coat, PSU including phantom supply for Β£200 !!! Switched IEC mains in with fuses and leds on all three voltages. Its mint and now I have my faithful GL up and running again. Though I would recommend opening up the desk and bypassing any of the blown circuitry of the internal PSU before connecting the new external one. Easy enough to do by removing the old PSU box and rewiring the 5 pin xlr