Thanks for your service.
You know your wife much better than 'we' do. I also used to use per diem to pay for a lot of toys when traveling overseas...Eat super cheap, pocket the difference.
Depending upon where your going (domestic or int'l?), you could easily set up a payment plan to cover your expenses in a couple of weeks.
If it were me, I'd let my wife know what I did and how I was going to pay for it by being uber super cheap on my next 10-20 days away.
أنا لست ارهابيا
.50 BMG: 1 Shot 1 THRILL!