Does anyone have an idea where to find 16S rRNA-targeted oligonucleotide probes for bacteria, for example : Nitrosospira spp. probe nimber " Nsv 443" and Nitrobacter spp. probe nimber "NIT 3"
A good source for probes is ProbeBase (http://probebase.csb.univie.ac.at/) that you can search either for probe names or organisms; the two probes you mentioned are for example listed in there. Otherwise, I had good success by simply goggling for the names or even the sequences when I came across probes without proper references.
Regarding the probe order, there are probably thousands of companies out there that can synthesize a probe for you. Again, just google for "probe synthesis" or ask colleagues at your institute about their experiences; a company that is suitable for us in Iceland (price, delivery time) might not be the best for you in Canada.
Probebase is a good site for getting already designed and published probes.
Since there are usually some outgroups and not all bacteria of the named taxa are targeted I would also test the probes (e.g. at https://www.arb-silva.de/search/testprobe/) or in programs like arb (http://www.arb-home.de/), where you can include your sequences (e.g. 16S amplicons), if you have any, and see wheter the probes fit. If there is no suitable probe available you can also design your own (e.g. on arb).