Sorry to break it to you Dan, but after trying different excuses eventually none will work... she'll catch-on, sometimes sooner than later.
What I found worked best...
First I reminded her how much I miss my old hobbies - racing, building my old muscle cars, drinking with the boys, my Harley, etc...
Then a few days later I mention to her I'm looking at an old car to restore or a new canoe or motorcycle that I want.
Now she knows I'm getting restless and feeling antsy. She realizes cabin-fever is setting in again so starts asking me what can we do that won't break the bank. I sulk and mope around the house for awhile feeling all misrable.
Finally I quietly say - "Well if I can't get the car I was looking at, think I can pickup a model so I can at least pretend I'm rebuilding an old car?"
Usually all she'll say is make sure we can afford it. She doesn't even ask me how much it will be any more, as long as I shut-up and stop moping around the house.
Note: Eventually she will say - "Stop acting like a little kid and just tell me you want another model kit. This sulking and moping routine is getting old."
Or you can just keep bugging her that you are in the mood for whoopie.
And with that my friend you can start to feel as though you might wear the pants in the house once again... someday.