Pair of
63 Volt (or higher)
4700uF (or higher)
capacitors.

Will throw 8 dollars at who ever can find any caps that can satisfy this.

12 bucks if they are 115degC rated.

rail gun?

Amplifier repair. I toasted mine. They aren't that big/impressive. ~3cm diameter ~7cm height.

(PROTIP: don't use external Soundblaster soundcards, they pop and click on initialization, total crap).

Sorry, the best 4700uF I got is a 35V. If you were asking for 470uF 200V or more I could hook you up.

Only ones I have that are even close are 470uF,200V and 2200uF,16V. All salvaged from ancient PSU's. I know they don't meet your requirements directly, but if you are creative enough, you might be able to assemble something that is comparable using Kirchhoff's law or something.

Capacitors add in parallel, and in series the voltages are distributed. So to put two capacitors in series you can double the voltage across them, but the resultant capacitance is halved. So to parallel two series pairs gives you the same capacitance at twice the voltage.