The links you included are not working. I use the Minolta 5600HS. This is an excellent flash and I highly recommend it. This flash appears to be the same as the Sony HVL 56AM. It is expensive, the 3600HS (Sony HVL 36AM) is also a good flash and a little cheaper. Try to find the Minolta versions as they are cheaper. Both of these flashes will work wirelessly with the Sony A100. Both can be found on ebay for more reasonable prices.