You might get more specific advice in the IGF/GH subforum. But anyway, you can use insulin syringes (around 28 gauge) to inject. Do it subcutaneously (right under the skin). A good location is in the belly fat. Pinch an inch and inject there.
Also, what do you mean by "disinfection?" The ghrp and the bacteriostatic water should already both be sterile. If you "disinfect" it, you'll likely destroy the peptide.
You can probably find the stuff you need on amazon.