Not sure about online stores... but as for shop I buy my dry cabinet from, I usually just go back to the shop I frequent most. I don't think the shops carry many different brands, so you may have to visit different shops.
Not too long ago, you can visit Funan to walk around the shops to get the feel of the different brand/size/price of the dry cabinets, but now, you might have to do abit of walking.... The shops have been relocated. The shops closest to the Funan vicinity might be Cathay Photo (Peninisular Plaza) and SLRR (Excelsior shopping centre) and further abit, in Plaza Singapura where you can find a couple more camera shops.
If you want to check out larger units, do visit Cathay Photo. The dry cab section is the same as the strobes and tripod/lightstands section. All on display there. Cathay only sells akarui, which I think are great dry cabs.
Many other shops carry Digicabi which the distributor is digihub. Some sell samurai, some sell eureka.
But you will notice that shops seldom carry more than one brand of dry cab.