I don't have any fancy suggestions, because much like you, I often went DIY. Because of my skin condition I've always needed a bidet, so convenience and utility was my draw, the fact I had to carry it with me everywhere my whole life since adolescence.

Pretty sure when I was first taught to do it by my chronic care nurse I was just using hospital peri-bottles. For a while I just carried a 50ml syringe in my bag and a bottle to draw water from.

But at some point (probably around 12 when I joined Scouts) I found these "bidet bottlecaps" at hiking stores, and I remember a time when I just had these bottle caps everywhere and would have plastic bottles with hair ties on them in random purses (I'd put a hair tie around the bottle to remind me it was not drinking water anymore) the brand name I'm seeing pop up is CuloClean, but I mostly see cheap screw on no-brand ones near the register at camping stores.

Now days I mostly DIY them with a lighter, a q tip and a pin.

Just take any plastic bottle lid, heat it up with the lighter to soften the plastic, use the q-tip to push the soft plastic to make a "nipple", you're basically trying to make the bottle lid resemble a baby bottle. Then take the pin and make a ~1-2mm hole in the side of the nipple. It's a good idea to sit down and hold the bottle and see how you're planning to aim the stream so you can plan where you want to angle the hole you're making in the lid.

I'm glad I found this method, because I like the little 250ml bottles of Quench Juice, they squeeze easy, hold just the right amount of water, and fit really neatly in all my purses (and the juice is nice too, lol). But the lid was never compatible with the bidet bottle caps, so now I DIY the existing cap of whatever bottle I prefer.

But in either case, you need to have a second, unaltered bottle cap to swap out after use, so the bottle is water tight for storage again. (though, you can always leave it empty and just refill immediately before use, then empty it completely afterwards)