There are Many great stores online Just to name a few Rotor Riot, GetFPV, and my All time favorite PYRO DRONE in L.A.
There are "kits" Available BUT I can tell you, You will be paying for either inferior parts or A frame that you will have trouble getting replacement parts for.
My advice to you is to do some research and talk to some builders {like you are reaching out for now} You will want to learn what parts go well with others how to choose the right stack or make your own and best still: How to get the thing to fly once you get it all put together. The program Most builders use is called BetaFlight and it has quite a learning curve on its own.
Its of course VERY do-able and would be a fun project I would be more than happy to help.
ALSO
The MOST IMPORTANT Advice I can give you is this:: Go to YouTube and watch all the Joshua Bardwell videos you can Find!!!!! I cannot say this enough!!
Oh I forgot to Add That Drone aint gonna be cheap. Depending on what you believe cheap to be!