I found these 3 that might be promising:

http://www.borntolove.com/frugal-travel.html

(Scroll down to Portable High Chair; very minimal instructions)

http://www.sleepingbaby.net/jan/Baby/chairseat.html

These instructions (sleepingbaby) are more detailed. Lots of other neat "sew for baby stuff" at this website. See link below this post.

http://www.canadianliving.com/Canadianliving/client/en/Crafts/DetailNews.asp?idNews=1666&pg=2&idsm=306

This web page (Canadian Living) has a downloadable PDF pattern for the roll up baby chair (and a diaper bag in the same PDF). The portable chair is similar to the pattern above.

HTH,
CMC
ps: I searched for stuff like "sew tie on baby seat" "sew portable high chair" "sew booster chair belt" and others I can't remember now, and just followed the few links that looked promising. Everyone has a different name for this!

Here is a link that might be useful: Jan Andrea's multiple baby-related crafts

I used to have one years ago made from placemats,i'm sure i got rid of it.It came from a magazine.
Kathi

Thanks, CMC. I finally got a chance today to look up those links you sent. The one from sleeping baby looks exactly like what I was searching for. Thanks again! I tried to reply to your email, but just realized I couldn't post directly back to you.

Mary

Mary,

You're welcome!

I used to have one of these when I was transporting a baby/toddler with me. It was very handy. I'd forgotten all about it (the "baby" is 23 years old now).

The one I had was made out of a mid- to light-weight denim (sturdy, yet not stiff) and I used it a lot. This would be a wonderful gift for new parents.

Thanks so much for reminding me about it. I have some new parents in my life who might enjoy one -- if I can only decide what its name should be!

CMC

I really liked the one made to go over the kitchen chair! I think I would alter it a little (I'm lazy). This is a great transistional piece from highchair to chair. And I think I even have room in the T-towell drawer for one!
Thanks for sharing this!
Woodsy