I think I read that there is only one manufacturer of polyquat. The people below just bottle it at different percentages so just pick the one that costs the least.
Here are some 60% polyquats which usually comes out to be the cheapest of the different percentages:
Aqua Guard Algaecide 60% Concentrated
Baquacil Performance Algicide
BioGuard Inhibit Algae All 60
GLB Algimycin 600
HDX Algaecide 60% Concentrate
In The Swim Algaecide 60 Plus
Leslies Algae Control
Kem Tek 60% Algaecide Concentrate
Omni Multi-Purpose Algaecide 60
Poolife AlgaeBomb 60 Algaecide
Pool Pals 6-0 Poly Algaecide
ProGuard 60% Algicide
ProTeam Polyquat 60
Vantage Algaecide 60 Plus
You can use this calculator to figure up what it costs. Polyquat is near the bottom. If you hold your cursor over the chemical name it will show you some different brands.
http://jfhtm350.webs.com/pool/ChemicalCostCalculator.html