Depending on your actual water source, you have a few options.
I use a short version of the home filter (
Housing). Now that you have the housing, you can choose your filter. I normally go for a .
5 micron solid carbon. That will take out most things. If your pumping pond scum near a hazardous waste plant, now your looking toward the ceramic filters. The down side here is, the smaller the micron, the more critical it is to prefilter it for debris. I cant seem to find the link where I got my ceramic filter from.
You can also get inline garden hose filters. The cheaper ones are activated charcoal but if you read the descriptions, you can find Catalytic carbon. I think
I pay $35 for my inline.
Remember, the better the filtering the lower the flow.
On my trailer I have the short filter with solid carbon that everything goes through. If I know I'm going somewhere where the water is suspect, I will pump it into my tank with my inline filter, run it from tank through house filter. That's good enough for the shower. If I want to drink it, I found a
counter top filter that takes the standard house filter. This is equipped with a .01 micron ceramic.
To be honest, I haven't felt the need to use it yet. Most of my trips I have access to city water. On a couple of trips, I pumped lake water through my inline to my tank but didn't feel the need for the 3rd filter.
Edited to add in links. The counter top filter I got was discontinued. The one I posted is similar.