Potty chairs for bigger children?

[WindyCityMom]

Does anyone know of a potty chair that's large enough for a tall almost 3yo girl?  Preferably with a splash guard of some sort ;) 

Everything I find is way too small, we have one that we just use as a step stool (it's meant to be a step stool as well).  Every product on the market seems to be marketed to 18 month old kids.

I *know* that there are kids out there who don't learn to use the potty until they're 4 or 5 even.  What do they do?

Using the regular toilet is not an option for us for a few reasons.  
a) DD is terribly clumsy and cannot get on it by herself even with the step stool (it's extremely dangerous actually, and falling down and then wetting yourself doesn't seem ideal IMO).
b) Our toilet is funky shaped and those little potty seat things don't work with our toilet, they don't fit and won't stay put.  Having her sit on the toilet without it isn't really an option because she seems to fall in every time she does.
c) My main reason, is because lifting her onto the big toilet is killing my back.  She's only 30lbs and I'm only 20 years old, but I've still thrown out my back on a couple occasions.  

d) Almost forgot to add that she needs to be able to go by herself for the time being right now because my 11 month old is going through (big time) separation anxiety and if I leave the room to be with her sister she totally flips out. 

So, I need a larger potty seat.  Anyone?  Ordering online is no problem, it is actually preferred.

[MissMaegie'sMama]

The Fisher Price "Precious Planet" frog-shaped potty has rave reviews on Walmart.com from parents of tall/older kiddos. My DH bought one earlier this year for DD2 before I read the online reviews, which I wish I had done before purchacing one. The potty didn't work so well for DD because she was 17 months old when we bought it, and it was a little too wide across the top for her to get on/off of easily (she ended up prefering the toilet with the adapter seat, go figure). If she had been older and/or taller upon initiating PL'ing, I think it would have been better suited for her.

A feature of this seat that you might appreciate is that it has no lid, so it's good for children who need to "go" with a minimum of assistance from an adult.

[JudiAU]

We use the regular size bjorn. My toddler is 45 pounds and at least 44 inches. Given the huge amount of time he spends on it (he loves to read stories there) it must be pretty comfortable.