Converting pants' waistband - Vogue 7933

I made a lot of clothes, especially pant/jeans before I had kids. Now that I have 2 kids, my body shape has changed a lot and some of the pants I made just don't fit properly. The waistband is a particular issue. I want to make them wearable again.

I have been seeing these 'comfort waist pants' sold in Reitmans (a Canadian clothing chain). I have never tried them on but they are pull-on style and do look comfortable and polished at the same time. I noticed that the waistband were cut on the stretchy grain just like the pants were. However, it seemed like there was something else underneath the waistband. Since I didn't own a pair, I wasn't able to find out.
I googled 'comfort waist pants' and found Myrna's blog (http://blog.myrnagiesbrecht.com/2010_03_01_archive.html). She owns a pair of these pants and actually took the waistband seam apart to find out what was in there. Apparently it has some sort of hard clear elastic sewn into the top of the waistband. I don't know where to find these elastics so I'm just going to wing it by sewing some non-roll elastic in my stash into a pair of pants that I made to see if that would work.

The pants that I will be experimenting on is this one (http://lovenicky.typepad.com/blog/2009/11/last-top-finished.html ) - Vogue 7933. It gapes horribly at the back if I don't wear a belt with it. I'm going to convert the waistband and see if it will improve the fit. Wish me luck!