Hi Chlo,
I ordered one of those Togu cushions and didn't get on with it. To me it felt like I was sitting on a couple of rubber hot water bottles filled with air and I didn't like the way it wobbled about - especially unstable for if you use it on public transport. Quite a number of people on this forum said they find the Togu really comfortable though, but, sadly, I found that the gap narrowed off too much near to the back of the cushion and it put pressure on places I didn't want it to.
They do a Dr Huff cut out on this smaller Putnams cushion
http://putnams.co.uk/collections/pressu ... ce-cushion (the choice of cut outs aren't pictured on the webpage, but they are all listed in the drop down menu) - However, I think that it would still be too bulky to be as discreet as you want a portable cushion to be (albeit the cover it comes in does disguise the cut out).
I too was interested in the twin peaks cushion, but decided against sending for it from the USA as I wouldn't be able to send it back easily if it didn't suit (because, as you know, I too am in the UK). The low profile twin cheeks sounded too firm and hard on the thighs for me and I thought that the 'trough' wouldn't be deep enough, but I noticed that the thicker version - which forms a deeper 'trough' - has a choice of medium (to extra firm) foam which I thought might make it more comfortable. Not an easy decision to make; you may have already done this, but if you do a search of past posts on this forum there are a number of comments about the twin peaks cushion.
The 'folio' cushion on Soula's webpage might be an option if you're willing to scout around for a suitable 'envelope' type bag or perhaps do some sewing and make yourself one
http://www.pudendalnerve.com.au/2012/11 ... f-you-can/ - It could be doubled over as shown and carried around like a clutch bag tucked under your arm or put in another bag. If you page down to the comments section Soula gives what she feels are the optimum measurements for it, i.e. to someone calling themselves 'MDNB' who was going to try and make one for their niece. (I was going to make one for myself, but I'm ok with my Dr Huff cushion and I use a Backjoy seat/cushion
http://www.backjoy.com/sitsmart-posture ... ne#start=1 in my husband's car, which I'm also finding to be good.)
I've sent you another pm.
Best wishes,
Dusty