B&Q stocks lots brands of silicone. The brand name of the one I got there is called Diall (Transparent) for bathrooms etc.
It seems to be identical both colour and smell to the aquarium type (which I also have) used by Glen Poynton the originator of the soft touch shrimp.
Silicone has quite a strong chemical odour while it is curing so probably best not fished for a day or so after tying.