If it's a production small-holding I would have thought a visit to the junta da freguesia, local famer's co-op or Ministry of Agriculture would be your best bet.
They'll have all the right contacts.
Otherwise from memory there is a garden centre on the left of the N110 leading out of Tomar south towards Torres Novas
Manei`s Viveiros e Jardins Zêzere Plant Lda
Estrada Nacional 110 42
2300-424 Tomar (São João Baptista)
They might be able to help.
Also - http://www.draplvt.mamaot.pt/DRAPLVT/co ... antes.aspx
There is also now an Agriloja in Tomar.
@39.5903846,-8.4075902,14z/data=!4m5!3m4!1s0x0:0xb85452c8773b712!8m2!3d39.592187!4d-8.40111"> https://www.google.pt/maps/place/Agrilo ... 4d-8.40111
I know from the one here in Torres Vedras that they stock a range of products you may require.
They also, sometimes, have the names of various specialist services in the area.
Be aware also that I believe the wells should be legally registered with the local "Administração Regionais Hídricas". You probably had that checked when the documentation for the property were validated by your lawyer. If not check out their legal status prior to contact Govt. Agencies.
Old article here: https://www.mundoportugues.pt/54225/