For bed bugs we recommend using Digrain Insecticlear. This is based on two naturally occurring insecticides found in plants: Pyrethrum is made directly from plants while Cypermethrin is a synthesised organic compound. The latter, in particular, is ideal for household applications as it can remain effective for a number of weeks.
A bed bug infestation is likely to require more than one treatment, therefore we would recommend buying a 5L Pack.