2 x Waterproof heat mats

HYDGOOHO Seedling Heat Mat 2-Pack Heating Mat Hydroponic Heating Pad Waterproof for Seed Germination Cloning and Plant Propagation – note that multiple variations of this product may be available, as such a different version may appear at this link

Also: Yeast Starters and Fermentation | Maintaining Fermentation Temps in Colder Weather

Inkbird ITC-308 – Dual Stage Digital Temperature Controller | Review | Inkbird Deals