Is there any topical treatment for toe nail fungus, thickening and discolored toenails?

Fungus. Agreed - first be sure it is fungus . With a black light fungus will fluoresce. I use a laser with good success (80-85%).
Fungus vs trauma. See a podiatrist to make sure it is fungus, sometimes trauma to the nail can cause discoloration. Topicals for fungus are 10-20% effective including tea tree oil, menthol( vicks), oregano oil, garlic oil, etc. In my office we dispense formula 3 which is more effective but only physician dispensed. Traumatic nails benefit from biotin or nail and hair formula vitamins and urea cream to thin them.
Topical . Topical treatments essentially don't work for nail fungus. There are anti fungal nail lacquers that are inexpensive and with really 0 side effects, but the response rate is about 10%. Nightly soaks for 20 minutes in dilute white vinegar (1/2c per gallon) probably has the same meager response. Oral antifungal medicine is really they way to go for this, but even that only has a 70% response rate.