here are some:
http://www.newhavendisplay.com/tfts-c-1.html

and more specifically this one might be interesting:
http://www.newhavendisplay.com/nhd57640480wfctxlt-nonstocked-50pc-moq-p-4304.html
5.7" of colorful iny tiny lights

Makes no sense to have a smaller screen but a higher price.

I'm working on basic calc engine with a no limit of precision. It's working good for moment, i can mul add sub until now without error.

Why re-write simple op like add ? Just because adder are limited by size of the physical adder. i'm writing a code that can add unlimited size of number. And the number is auto-sized to the minimal size needed.

In case of irrational number there is tips for detect and stop the size. And i'm gonna use a smarter approach.

i work mostly the wednesday morning, so next time i aim to code divide.
My basic engine aim to be able (8^3)! without bug and don't do an approx like wolfram, but do the real calc.
the code is C++, is writed for console check in visual studio 2012, all the code is able to be compiled by gcc++.
So aimed to be portable for any CPU & OS.

I'm not working for optimisation now, just working & check working with asserts and visual inspections.

My forum is down, because i did a mistake on the server so until i fix it, it's normal. And as nobody help, this is not very important that the forum come back very soon. so when i have time to install apache again.

So code is growing ...

ok now the systems is working with multiples Atoms, so i've done a test on 199! and it's clearly the good answer.

now i'm gonna integrate Xint to do random asserts to be sure that truely working.


@+

Building a CAS from scratch is a very hard task, but in my place I just port the Maxima or any well tested CAS. Afterwall I agreed in your choice to use Linux as a core operating system of your prototype, but if it will be a open calculator, then any official repository should have the Maxima as an alternative CAS engine.
One of the big mistakes in any retail calculator CAS in market is the unability to evaluate contour integrals, residues of functions or addicional special functions used in engeneering courses.
I hope will add this functions someday.