Glendoick is my favourite source - but there are other Rhododendron specialist of course and some of the specialist alpine nurseries like Ardfearn, Edrom, Hartside, Aberconwy etc will also have some little rhodos that will prove to be good show plants.
There are a good number of little hybrids but many judges do favour a species.
R. keleticum, impeditium, campylogynum, nivale, pemakoense , lepidotum, the Ledum/Rhododendrons such as groenlandicum, Rhodora canadense, sargentianum, cephalanthum..... all come to mind as ones we had success with in the past.
Hybrids like Egret, Merganser, Rose Elf, Wren, Plover, Sarled and Maricee - two crackers, those - how's that for a starting list? You'll notice a predominance of Cox'es bird-named hybrids in there !