If you want an insulated vest/gilet then most outdoor brands will have one.
You need to decide what time of fill you want
– down – would suggest not
– non breathable synthetic, like primaloft gold/one – warm and nice
– breathable synthetic, like polartec alpha, less warm but much more breathable
Then the outer and inner fabric will make a difference to how much wind gets through, so will also have an impact on warmth
I have loads of gilets, it’s a problem! Alpha, primaloft, down and normal windproof, plus insulated as per normal and insulated front.
For riding at low pace something insulated front and back will be fine. For most pacier rides something insulated on the front and non-insulated (and ideally non-windproof) on the back will be great. There are a few options available. Cycling brands like Rapha do them, but you can find running ones at a much better price that are sometimes more versatile. I have an Adidas Terrex one, and as it’s for running and not cycling has hand pockets and a chest pocket, which for the type of use it gets is dead handy