I do not know much about charging Li-ion.
Find a charger(s) that know how to charge this chemistry and voltage (24v).
From there, the charger will have an input voltage range. For MPPT shoot for a panel(s) near the upper end of max input voltage. For PWM, shoot for something about 25% above your battery voltage (someone correct me if there is a better number here!)
And big cheap panels can normally be found on craigslist or eBay. Just stay within input voltage and input amps of your SCC of choice. If you find some and want a sanity check, post links, someone can likely help.