AlainDelon: There are a few places that carry suitable, reasonably priced, replacement power supplies for the i-Opener. The most reliable source is Jameco, part #169076. This is a 20v, 5amp supply (50w) that has a adjustable output voltage. It is only $20.00, but it is rather large. However, it always seems to be in stock.
Another option (IMHO a better option) is to search eBay for laptop power adapters. If you look long enough you will be able to determine what laptop has similar power requirements. Sometimes the specifications of the adapter are included in the description, sometimes you have to look at the picture and read the specs from the back of the adapter. I've purchased quite a few adapters this way in the $15-$40 price range. The advantage to the notebook adapter is that they are usually fairly small (physical size).
The last option is to check out the surplus sites like compgeeks, allelectronics, hitechcafe, bgmicro, etc. These can be long shots, but sometimes you can find what you need for cheap.
If you are not a CB like me (CB=cheap bastard) then there are places like Targus, Port, APCC that sell expensive (but very nice) replacement adapters.
Electronics run on smoke, if you let the smoke out they won't work