1. Musicnotes: Search for "Inspector Gadget" on Musicnotes, an online sheet music store. You can purchase and download the digital sheet music.
2. Alfred Music: Check the Alfred Music website or catalog.
Alfred Music is a known publisher of educational and popular sheet music. They might carry the 'Inspector Gadget" theme for various instruments.
3. Hal Leonard: Hal Leonard Corporation is another notable music publisher. Visit their website or music retailers that stock Hal Leonard selections to see if they offer" Inspector Gadget" sheet music.
4. Online resources: There are free websites and sheet music repositories where you can search for public domain compositions and arrangements. Some sites to try includes:
- Internet Archive
- IMSLP( International Music Score Library Project).
- Free Music Archive