g. siamensis is a bit vague.. could be a gekko or a shark!
do you mean C. Siamensis - Crossocheilus siamensis AKA siamese algae eater?
I know trimar aquariaum delivers and has a good reputation. I got a CAE off them - excellent service.. and only £10 postage - certainly cheaper than the petrol it would take for me to drive there
or alternatively.. do you mean - Geophagus surinamensis.. in which case i dunno about them .. sry