Ok, which latest flashcards and how do I know about the backlight ?

 

Your only real option is a flash cart.

Top of the line these days are the EZFlash Omega and the Everdrive lines. Both should be in the review section here.

You might still find an EZ4 out there in some shop. They might not have as much in the way of features but "can they play essentially every game as it would on hardware, and the exceptions https://gbatemp.net/threads/buying-a-gba-flash-cart-in-2013.341203/page-18#post-4756995 being fairly readily managed?" "Yes, yes they can".

Everything else. If it is for a GBA-SP then don't bother. If it was for a DS a DS flash cart and a 3 in 1 might be an idea but this ain't that and it will not be easy to use with a SP.

SP model? None ever saw blocks on anything, however the AGS 101 model came with a backlight and thus is the more sought after revision of the device (naturally it was released before the whole thing was shut down and in fairly limited numbers). There are some methods to retrofit 101 screens to other GBAs (most go for the original GBA but you should be able to get kits for the normal GBA-SP too). Don't quote me on this but you should be able to mix and match case parts if you did decide you wanted a nice older colour scheme which the 101 never got released in.
Alas with the typical quality of online photos you are not going to be able to tell that easily, indeed even in person it can be hard. To that end you are left with looking at serial numbers for such a thing. You might get lucky and find some clueless kid at a yard sale (our show off your new crap thread has several such occurrences) to flog you one for $10 or something but don't count on it.

 

Ebay and Amazon often have them, despite their own rules that say they are not supposed to be sold there
As for dedicated websites, a few great classic ones like nds-card, shop01media, ... are still going fine

 

Ok thanks I will take a look.

 

is it possible to swap out the old screen without the back light, for a AGS-101 screen?

 

ahh, okay thanks again.

 

There are many ways to load small homebrew on your gameboy advance without a flashcart. They involve building a cable to connect the multiplayer port to PC. With the right software you can even dump your games. If you have a gamecube and a GBA-GC cable you can load homebrew to the GBA from the gamecube (assuming that you have a way to boot homebrew on the cube). I think you can do the same with a wii thru the gamecube ports. Another way is to use an e-reader and load homebrew thru printed cards (yes, printed with paper) and probably it should be possible to load something also using the official MP3 adapter called play yan altough I never see an homebrew for this device.

 

You can just buy a 001 model, it saves you a lot of money and it works fine.

 

Sure! Thwe only reason to go for the SP is the form-factor. My girlfriend says size does matter... (I'm in the sp category)