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.
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
Use a universal adapter.
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.
You have to buy one.
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.
One type of headphone adapter is a 3.5mm plug. These are commonly used for portable audio equipment such as mobile phones and portable stereos and are almost universal.