Yeah I second what everyone else is saying. Just know how to use CDJs and take a thumb drive with you or a CD. That's your safest bet.
audio 4 / 6 that will get minimal use
numark mixtrack on the cheap
something else ...... but what ? old vci maybe ?
2 x Decent Thumb drives = $10
Backup = Priceless
Of course if you have a backup solution in place you will NEVER need it, if you dont have a backup you are bound to have eventual equipment failure.
Sometimes its refreshing just to play on CDJ's for kicks and ditch all the fancy stuff anyhow.... I did a gig a while back and they provided CDJ's (I normally use Ableton), ended up playing almost the entire 8 hour set off 4 mp3 CD's I'd burned as backup, gave me more chance to be sociable n' stuff .