producing quality research in non ideal laboratories
You target enough problems in your lab that it is probably worth your effort now to look for other opportunities rather than just accept the one that has fallen to you. It may be that you are well-enough placed to move to another university/lab and also obtain funding. 

In some fields, students work more or less alone, independent of their advisors, but it doesn't sound like you are in such a situation. 

But you can probably contact a few people in your field, not to seek a co-advisor but a new position entirely. You can do this discretely at first until you get a sense of what is possible. 

I'm guessing that staying in your current situation won't be terrible. But you might be able to do at least a bit better. But you won't know until you look. 

I'll also suggest that a co-advisor from another university might not be able to give you the attention you need. The nature of the relationship and the distance will work against that, as well as raising possible conflicts with your advisor. So tread carefully in that direction if you decide to go there. 



I should add that before you condemn your current lab too severely, you should also look to see what has happened to other students who have graduated out of it. Are they developing the careers they hope for? Do they have good positions? If that is so, then the lab is a success, not a failure.