Firstly, I know my bid is well above your budget, but this is a realistic bid for the work you seek to have done in the United Kingdom.
I have within my local area Boots, Lloyds, Asda, Morrisons, Sainsbury and Tesco major pharmacy groups. Please note that my bid is subject to obtaining formal permission from the management at each store, and that is not easy in this country. I also have Superdrug nearby, but they may not carry such a large range as they do not have a registered pharmacist permanently based in my local store.
I have personal contacts at Asda and Sainsbury.
All of these companies will require the researcher to carry a DBS certificate (criminal record check) and full public liability insurance. I have both.
This work will be carried out locally to me. If you wish the work to be undertaken in London then the fee will be somewhat higher to cover time, travel and parking.
Any questions please ask.
Kind regards
Barney Douglas
Hangleton Lane Studio
West Sussex