I don’t know if it would help, but I used to recite my images as I walked. You can set an easy pace at first, like one image every 8 steps, working up to one image per step. Once you can recall one image per step, start reciting them backwards.
Try doing only 00-09 at first. Then switch to 10-19. Then 20-29. Etc.
Another idea: if you have paper flash cards, maybe try carrying around five of them in your hand and checking them every half hour throughout the day. Once you know those five, put them aside and take five more cards. Keep rotating them until you know all of them.
(See spaced repetition and the Leitner system for ideas on how to review the cards.)
There’s also a post here with some ideas: How do I memorize a mnemonic number or card system?