Hi Ferg.
There ara many ways to go with your backpack, depending on how accurate you want to be, and the size of your buget.
Over here at the MEPD you will find the most up to date info, but also a few alternatives that were common practice before specific info became available along the time.
So... a few tips here:
-Wipe bottles are ok. As long as you find them. I would think that there are several sizes dependingh on your local market. One hack... don´t just look for baby wipes. I found mine on the car care section. They are actually armor-all wipes. Found those fitting for my pack.
-The size you need will mostly depend on the overall size and look of your pack. I mean, of course there is the desired size and look. But depending on where you source your frame and seedtrays, the size of the rest of the parts can come up accurate or odd... So. If this is your first try, unless you want to go uber accurate from day one, give it a try... mix and match, and if you don't like how it looks or if you do, go with it. I mean, of course we aim for accuracy. But since there is still some debate on a few of the original found parts (like the bottles) and even the seedtrays, there is still some room for interpretation.
-Navigate the board. Dig up some old threads and info. It is not just a matter of getting the recipe, but to actually live and understand where things come form and how we got to learn them. It was years and years of peope like you and me playing detectives trying to find out what each part of the TD armor is.
Most production armor, props, and weapons have survived till today, so there are many ways to get a sense of how real costumes were put together. Not the ANH Sandtrooper backpacks. This is probably the only part that was not conserved after production. Since they were stripped off parts and refursbished for the rebels backpacks in Hoth. Not a single pack survived... so it is all a matter of investigating, trial and error, more investigating and a lot of love for the hobby.
Hope this helps.
And, the board might be slow... but all the info is right here. Even if no one replies, you can find all the info you need in these boards.
Saludos.