Why not a small explosive laced with a chemical weapon like VX or sarin?

While still hard to get ahold old, explosives are generally more accessible than legit chemical weapons?

Barring mad scientists with chemistry sets and a grudge. And even in such a case it may be safer for said mad scientist to homebrew explosives in favor of chemical weapons.

Making TATP is fairly easy and all the precursor ingredients can be easily bought and they are often unregulated at all and untracked unless you are looking to make a bomb big enough to level a few city blocks.

TATP is so unstable, that even though it is chemically speaking relatively straightforward to create, it is actually quite difficult to produce while staying alive/in one piece.

It is sensitive to temperature variations, high temperatures, ANY open flame, ANY friction (rubbing your fingers together is more than enough), ANY shock, such as failing to set down a container, dish, or vial slowly enough, and having a small static charge in your body will also set it off. Because of this, TATP actually has no current industrial or military application.

Yes but that’s also because industry and military do have access to better explosives. Terrorists and ATM thieves seem to actually resort to this method due to its ease, says my 2-minute google search, with (mixed) success.

TATP also has another advantage as its not a nitrate based explosive it cannot be easily detected using field kits.

Explosives are relatively easy to make at home for technically minded attackers. Sarin and VX require much more difficult-to-obtain chemicals, or several more difficult synthetic stages, and are much easier to accidentally kill yourself with. The only criminal group I'm aware of that actually made their own nerve gas was the Aum Shinrikyo group:

https://en.wikipedia.org/wiki/Tokyo_subway_sarin_attack

What about ricin? I thought that it was relatively easy to source from castor beans.

I too watched Breaking Bad...

You need to eat a lot of it. The only reason anyone even sees media about ricin is because it really isn't as potent as it's portrayed, and it stops copycats from using what they see on TV to kill a lot of people.

When I was a kid my mother would give me a tablespoon of foul-tasting castor oil as a laxative.

Since learning about the ricin connection it's always been a source of bemusement whenever I think about it.

Edit: presumably by 'a lot' you mean milligrams (by ingestion) and not micrograms. From my understanding eating 100mg would be a certain death sentence.

Maybe some NaOH? Not deadly, but would certainly be very unpleasant to have explode in your face.

Those seem like they should be pretty hard to come by, but there are some toxic gasses that result from not-too-exotic chemistry, which can effectively kill with a whiff.

I could be wrong about this, but off the top of my head can't you make chlorine gas by mixing bleach with a strong acid?

acid not necessary. ammonia.

The difficulty with toxic gases is in the delivery method. For example Chlorine gas at hundreds of PPM still takes several minutes of inhalation to be fatal, and it is a strong irritant so everyone will know it's there and be trying their hardest to get away from it. So you either need to trap someone in a very enclosed space or release ridiculous amounts of it very quickly. Viable for trench warfare, but not much else.

Realistically you need something odorless (=exotic enough the human nose hasn't evolved to detect it), fast acting (=highly reactive/unstable), and dangerous at low concentrations (=likely to kill you while making it).