Mopani wood is good. But this will generally only lower the pH slightly and over a period of time.
Peat is added to the filter media (can be placed in some tights) but this will discolour your water. Not harmful for the fish, but some people don't like it.
Have you tested your tap water when it stood for 24 hours ? How old is your test kit and how long has it been open ? Tests usually only lasts around 6 months once opened (within the "best before" date).
You might also want to take a sample to your shop to test.
CO2 is very tricky and unstable unless you get a pressurised gas bottle (expensive). The DIY method is a pain as it has to be refilled every 5 - 7 days or so and has to be checked daily.
RO is also a very expensive method. You can get various units to purify your tapwater, but you have to attached this to your pipes and need some large container to collect the water. A lot of water goes to waste in the production of RO water.
You can also buy RO water from most fish shops - but in the long run this is also expensive. And you obviously need to regularly go to the shop to buy new water. Not feasible if you don't have a car or a large tank.
Else, keep fish that don't mind a high pH. African Cichlids love it.
Though that said, my pH can sometimes push 8.2 and my community fish are absolutely fine
Edit:
This article on Aquarium water chemistry might be useful as well.
