I confess that pigeons are my least favorite bird. I personally hope
my research will help you with your problem.
I found a large number of stores which sell their products online.
Alternatively, if you are interested in a specific product, you may be
able to purchase it at a local hardware or "Home Depot" type of store
by asking for it by name. You may also be able to construct some of
the solutions yourself.
You can start by searching my favorite web search engine, Google(!)
Using the terms
You will get a huge number of relevant hits. It appears that there is
a large and vigorous market for mechanisms to keep pigeons away!
It may help to start with an overview of pigeons and pigeon problems,
Pigeons by William Kern
In this document Kern broadly discusses the various types of options
for dealing with pigeons including trapping, the use of barriers,
poisons, chemical repellants, sound repellants, etc. This is a
factsheet put out by the University of Florida.
The results of the above search generally led me to a number of
specific commercial products for pigeon control. One of the more
interesting ones that I found was:
Hot Foot Gel
Hot Foot Gel is a tactile repellant which can be applied to surfaces
in order to repel pigeons. Apparently pigeons don't like stepping in
Most of the companies I found give a number of different options at
various prices, for example:
Non-Harmful Pigeon Control
4 the Birds II
Physical barriers are the specialty of these two companies:
Bird Barrier America
These are just a few of examples of what you will find. I recommend
you do the search using the terms "repel pigeons" as suggested to find
the larger number of options available to you if these specific
recommendations don't help.
You can also use search terms such as:
pigeons and dislike odor
This, too, turned up a number of sites that sell vermin repellant
devices and chemicals, such as:
Another particularly interesting site if you're versed in chemistry
This paper discusses the use of the substance cinnamic acid
(trans-3-phenylprop-2-enoic acid) which was found to repel birds from
eating plants. If your problem is about pigeons eating your plants,
this might be for you.
As you can see, you have a lot of options available to you and I wish
you luck in keeping your apartment balcony pigeon free!