...will bring my own, but out of curiosity, do they themselves carry them in times of need?

If you need a special fit however, they might use yours, but remember to bring them in a sealed box.

I've never heard of an agency providing them.  ???   A provider is within her rights to refuse to use condoms supplied by others...  there are internet ledgends about guys tampering with condoms.  However, carry a sealed 3 pack continues to be a good idea...  avoiding certain scams & other emergencies like her last one needing to be replaced.  
I started bringing my own seal 3 pack when my ATF called when I was enroute & asked me to buy some...  offered to reimburse me...  the cost was not the problem.  Getting off the highway in a strange neighborhood & trying to find a store...  ending up with a lesser choice than I prefered.  Much easier to buy at my convience.  I leave any extras.

....I always keep male and female condoms at my incall, and bring both, when doing an outcall.  If a gentleman has a favorite, he must bring them in a sealed box.

Interesting. I always bring my own. Never thought to bring a sealed box because I buy large quantities. Never had a problem. And I'm going back many years. Never had a provider reject my hats because they weren't in a factory sealed box. Good thing too since I really need the particular brand that I buy.

Most providers prefer their own choice.  I would think that if a guy needs a special type, size, etc., that many would use what he brings, with requirements.  As far as agencies go, I have no idea since I have never used one.  My guess would be that the individual providers would have their own preferences as indies do.

being in a red light area. A condom it more proof you want sex.

So it's undoubtably true that some ladies require this (and Kelly does indeed indicate this above), but for what it's worth, I always just bring a few loose condoms with me, and 90% of the time we use those.  The other 10% of the time the lady uses her own (which I'm fine with, because it means she has the correct size).  So, I wouldn't worry too much about the sealed box thing.  And most likely, if she is the type who is so concerned about having a sealed box, then she will ALSO likely be the type who will have a good inventory to fit all size gents anyway! (thus no need to bring your own).

...cogent answers or don't post at all. This junk on the General board is one thing but it has no place here.

why not just bring a few that are still sealed in their individual packages?

Seems a bit overkill to have to have a sealed box Everytime and a waste.  Sometimes I have ejaculation issues and I prefer certain condims not just becsuse they are thin.  But becsuse some are made with ribs or texture on the inside in only one or two areas that stimulate me.   And I will buy larger quantities to save money.