A proverb usually contains some core of popular wisdom, as in "A stitch in time saves nine". I can't see the "wisdom" enshrined in "Such as it is, you are welcome to it". How would you use this phrase, and what would be its deeper meaning?
There may be some English equivalent, or it may not in fact be what we would call a proverb.
Newt's suggestion doesn't sound like a proverb to me.