Brian, thermal sailplanes are stocked by the larger hobby shops in Hong Kong such as the following but the choices are rather limited.
Tak Cheong R/C Model Co.
252 Hollywood Road,
Sheung Wan
Hong Kong Island
Tel: 2857 5021, Fax: 2857 5034.
Radar Company Ltd
Flat A, G/F.,
Grandeur Building,
368 Kwun Tong Road,
Kowloon, Hong Kong
Tel: (852) 2739 0577
Fax: (852) 2739 0717
URL:
http://www.radarrc.com
Seious sailplane modellers in Hong Kong whom I know of all bought their planes in Europe in person or through mail order.
If you buy one in Hong Kong, I'm not too sure if the savings, if any, are large enough to justify the hassle of buying such a bulky item and take it with you to the US.
On the other hand, radio gear should be a best buy for you. I think Hong Kong's prices for them are much cheaper than in the US. Bands such as 29, 35, 36, 40, 41 and 72 Mhz are used in Hong Kong (some illegally but the rules aren't strictly enforced) so you should have no problem picking the appropriate band.