Hi Jason, do check with your existing insurers to see if any elements of your policy are still in force despite the FCO advice against travel to Spain. Voyager, Battleface or Versatile are companies offering travel insurance for destinations that have FCO advise against all non-essential travel.
You should also make sure that your E111 / EHIC cards are up to date https://www.nhs.uk/using-the-nhs/healthcare-abroad/apply-for-a-free-ehic-european-health-insurance-card/
The Canary Islands have provided a free insurance for visitors who have a positive case of Covid diagnosed whilst in destination. This is to cover medical expenses and an extension of stay for up to a maximum of 15 days staying in regulated tourist accommodation.