Copics and pencils use completely different techniques so you won't find one product that blends both.
The Copic colorless blender is not a blender in the sense you might expect. Marianne Walker (Copic Queen) says it should be called something more like a "color pusher arounder" :lol: You do most of your blending with the markers themselves by layering colour and then using the lightest shade to even out distinct edges. Try Marianne's blog (
ilikemarkers) for lots of information, technique hints and tips etc.
Pencils blend with Odorless Mineral Spirits (such as Gamsol or Mona Lisa) but not everybody wants to use that kind of chemical. Some people get great results using baby oil and if you search the forum for "goo gone" you'll find lots of info about using that as a substitute too (I can't comment on that one from personal experience as it's not something we have in the UK).
Your best best might be to have a look at lots of example of colouring with the two different media and decide which you want to go for. Even better if you can find a LSS that has classes or try-out sessions and see if you can get to play with both markers and pencils before you invest your money.
HTH!