How to control bacterial infection in a plant tissue culture?

I have very big problems with some bacterial contamination in my cultures, Tuberous Begonia, Echinacea Purpurea, Lilium Ledebourii. Not all of my cultures are infected but contamination reduces my proliferation rate and wastes reculture time and efforts. I have used Gentamycin at a dose of 250mg/L without good results. I use NADCC to sterilize infected plants. It is a very nice sterilizing agent but doesn't kill internal contamination. I don't have access to laboratory equipment (laminar hood). I have several kinds of antibiotics such as rifampicin, streptomycin, cefotaxim, erythromycin and I must have an autoclaveable antibiotic. I know that there are many biocides like PPM or Kathon but sadly I can't buy them because of a trade embargo against Iran.
I culture everythings in test tubes and falcon tubes because this way contamination is low in none sterile condition .this is my hand made growth room
http://www.ishs.ir/4.jpg . this way i don't need support of any institute and work private .