Based on this score, the best time of year to visit Nakuru for hot-weather activities is from mid January to mid March, with a peak score in the third week of February.
Step 1 - Rinsing. Especially for larger neoprene-based items, you should be rinsing for at least three or four minutes straight after every use. Try to rinse using clean, fresh water applied in a directed spray. A shower head with a removable handle will work for smaller items, so you can direct the spray in the tub.
Otherwise, the only thing you could do would be to scan the shirt, print out the scan onto a piece of iron-on paper (you can buy it all over the place now), and then cut it out and iron it onto another shirt. Or you could check eBay for that shirt.