A flux capacitor would be my most desired purchase.
I can build you a Flux Capacitor for Bitcoins
Seriously. I am Electronic Engineer, and here is the one I have been tinkering with and improving for a while.
Its actually more finished than this photo (which was taken a couple of months ago).
Notice that this is a much more advanced model than the 1988 BTTF Version. Tech has moved on since then you know
Most of the worlds Flux Capacitor builders are of the "Cargo Cult" variety, slavishly duplicating the color of the paint, the stickers on the vacuum relays and the placement of the screws.. How trivial.. If they *understood* how it worked, they would realise such things are irrelevant to the operating principles.
This one includes..
- an inbuilt Arc Reactor for a power source (No Plutonium or Mr.Fusions needed for the Gigawatt supply),
-Flux Compression Rings to eliminate the need for a stainless steel shell around the operator (No Delorean needed)
-Nixie Plasma Wave guides for inertial space/time coordinate correction so you dont suddenly find yourself out in space or underground when moving temporally but not allowing for the distortions around any Kerr Spacetime Metric (http://en.wikipedia.org/wiki/Kerr_metric)
-Microprocessor controlled PWM modulated Electroluminescent Coils for adjustable containment of the Temporal Field Radius so the displacement effect can be tailored to take as much or as little of the surrounding environment with you as you like.
-Bluetooth Interface so the Field Parameters can be controlled from your Android Smart phone, making all those clunky TouchTone Keypad and 7-Segment Displays obsolete. We're talking touch screen interface and voice control here man. "Scotty, beam me forwards !" spoken into your phone will have trigger the forward displacement field phase shifts and so on.
Heres the circuitry on the back as it was a couple of months ago.
If youre interested, I will take some more up to date photos..
Unfortunately, I got a bit enthusiastic and couldnt help testing the Triple-Dimension-axis capacitor discharge displacement functions before the
EL Field Containment Coils were operational, and ever since then, things have been a bit .. *weird*.
Im not sure exactly how large the test field was, or how far it extended out from the center. I may now be living in a slightly different quantum time signature parallel reality than I was before, but I havent been able to think of a test that will prove the matter conclusively. I tried putting my Cat in a box, but it just howled and scratched me when I let it out, so that didnt work.
I can build you a duplicate model if you like (although its taken a *lot* of work and 6months + of time so far as you can see from the photos, so it wont be cheap, a few million BTC should cover it, after all, you will only need *1* coin to operate the whole words economy on in the future
) - and I cant offer you an instruction manual if you do want one, so any unintended reality distortions, delusions or other things that may result from its experimental use are thereform your problem. 
