This is a universal adapter a should work.
Yes you can use a universal Rf Adapter with your gamecube. One particular brand is called Mad Catz Universal RF Adapter.
You need a universal adaptor. You can find one at http://www.amazon.com/Universal-World-Travel-Charger-Adapter/dp/B001MGUB9Q/ref=sr_1_2?ie=UTF8&qid=1300903754&sr=8-2.
A universal AC adapter can be purchased from The Source, Future Shop, Best Buy, Staples, Walmart, Target, KMart, Sears, Grand & Toy, Amazon and Office Works.
One can buy a Scart adapter from the local store and online stores such as the following; multi scart adapter on amazon, Tesco scart adapter with switcher on Tesco, and delupe.
You can buy a firewire adapter from stores such as Best Buy and Walmart. Alternatively, you can also buy this item from retailers such as Amazon and Overstock.
Use a universal adapter.
Vnsport Universal Travel Adapter 45W PD Support fast charging and QC3.0 USB Type-C for USA EU UK AU Plug all in one 3 USB universal adapter travel charger 200+ Countries
You have to buy one.
I would go to Best Buy or Amazon.com for those. You can get a NETGEAR - Universal Push2TV HD Wireless PC-to-TV Adapter from best buy for only $99.98. On Amazon.com you can get a Sewell PC to TV (VGA to RCA) Converter w/ All-in-One Cable for only $29.95.
If you go on amazon you can find a universal adapter that costs very low. It is a quick and efficient way to get one. You can even look for one that has free shipping.
Buy a new one.