Value Village is a good place to start if you're looking for a costume. They have a very large selection. If you're looking online, it can get a bit pricey, but Ebay would be a good alternative.
How adorable. You can find affordable and adorable dog costumes online. You should check out www.buycostumes.com or www.costumecraze.com. They have a huge selection.
Amazon.com will give you plenty of choices to make a memorable party for you & your friends. Simply go to Amazon.com and type in what type of costume you are searching for in the search bar. Whether it is Saturn or Mars you will find the best costume online at an affordable price.
You can try your local seasonal halloween store, or Toysrus or Party City. Cat customes are adorable and you can usually find a more affordable selection online at www.buycustomes.com
There are a great deal of websites that offer cute, affordable animal costumes for a reasonable price. Try www.wholesalehalloweencostumes.com, it has great deals.
I couldn't find too many sources, but there is http://www.wondercostumes.com/Police_costumes-qspolice.html if you want to buy it online. Making your own costume is also a possibility. You can make it like you want.
You can go to insurance.com to find good and affordable life insurance online
There are several great online stores that offer cool costumes at affordable prices. Try www.buycostumes.com/Hippie or www.costumesupercenter.com. Or you can try local stores, if you don't want to buy online.
Party City is an excellent place to look for a police officer costume. You can also find one at newegg.com for $31.95 or http://www.halloweencostumes.com/police-costumes.html
Understanding you've asked about buying a ready-made costume, still, I can't pass up mentioning how easy it is to do it at home. If you decide to try it, you might take a look here: http://www.essortment.com/halloween-costume-projects-make-own-cheap-cat-costume-52154.html. If you're determined to buy your cat costume some sites offering affordable options are: www.zoogstercostumes.com/landing/cat.php www.bellaonline.com/articles/art63742.asp
One can find an executioner costume for Halloween online at websites such as Amazon or eBay. One can also make their own executioner costume by following tutorials online at YouTube.
Wal-Mart or Spirit Halloween store are probably going to be your best bet for what you're looking for. Both are not costly, and carry a wide array of costumes.
You can find reputable and affordable exterior painters online. People can find these painters at www.certapro.com/exterior-house-paint-estimator.aspx.