If you want a cheap IR remote, on ebay any of the following Roku tv brand remotes would work on your Sanyo: Tcl, Onn, Rca, Jvc, Westinghouse Magnavox. For sure Sharp and Hisense won't. When looking for a Roku tv remote look for power key, and crescent moon key(Sleep timer).
If you want to upgrade to wifi remote roku sells one:
I tried to search this website for a replacement but it just has the new one with voice command and doesn’t tell me if it works with all the tlc roki TVs I’ve had this one for 5 years? I need more information on the remote and there is none. The Model number is 3S3750
Please contact your TV's manufacturer directly to report this issue and request additional support. Each Roku TV manufacturer provides direct support and warranty services for their products running the Roku OS.
If you need a replacement remote for a Roku TV, you would need to contact your TV manufacturer. For a list of Roku TV manufacturer contact information, you can visit our Community post here: Contacting Support for Your Roku TV