People from La Gomera have the highest amount of Guanche ancestry of all Canary Islanders, apparently:

Island N Average NW African ancestry
La Gomera 7 42.50 %
Fuerteventura 10 21.60 %
La Palma 7 21.00 %
El Hierro 7 19.80 %
Lanzarote 13 16.40 %
Tenerife 30 14.30 %
Gran Canaria 30 12.40 %
Total Canary Islanders 104 17.40 %

The samples from that study are not publicly available.

Maybe someone has a GEDmatch kit number of a person with all 4 grandparents etc. from La Gomera?