I have Meade 2x Telenegative (doublet), it is not bad, I bought it on ebay (from China) for ~$30 10 years ago... Recently I tried to use it on Mars with my 10"and Canon 60D, results were quite good.
I can see that
that model is now selling on ebay for 2x as much....
Don't spend too much for new Barlow, the performance of your scope doesn't warrant expensive accessories. Sort the focus first, because you will most likely have the same issue with another barlow anyway.
Perhaps the better option is to buy a short eyepiece (Ortho?) (4~5mm FL)