Hey there Jenna,
Welcome back to planDisney and thank you for your question! I absolutely love the history behind Oswald the Lucky Rabbit and it's always fun to get to spot him when he visits the Disneyland Resort.
The merchandise offered at the Happiest Place on Earth does fluctuate and change throughout the year, and there typically are not specific announcements on exactly what you're able to find for certain characters.
However, I think your best bet on finding Oswald merchandise - if it's available on your next visit - would be in
Oswald's or
Elias & Co. on Buena Vista Street in Disney California Adventure Park. If you don't find anything there then you might want to check the
Emporium on Main Street, U.S.A., in Disneyland Park or
World of Disney in the Downtown Disney District.
Between those four stores, you should be able to find Oswald merchandise if there is currently any available around the Disneyland Resort.
Thanks again for your question, Jenna, and I wish you luck in your search for some cool new Oswald the Lucky Rabbit merchandise!
Have a Magical Day,
Greg