I have heard that M4M or Magic for Men is outstanding. (pun intended)
You can buy a number of places but guys I have talked to get off eBay.
You can also read about it on www.magicformen.com/‎ .

http://www.drhansen.com/2011/06/16/pistachios-improve-erectile-function

I've used sundrug and best generic pharmacy and ordered them online.

You should be able to split the pill in half or thirds and still get it to work.  Works for most people?
Best of all worlds, lower cost on a known safe medication.

There are no generics available for any of the ED drugs Cialis, Levitra, or Viagra. Check the manufacturer's web site for the drug (www.cialis.com or www.viagra.com or www.levitra.com) and all the companies offer coupons for either a free trial or money off of the prescription.

A 100mg tablet of Viagra is about $30, but if you score it in the middle it can be broken in half. To quarter it is a little more difficult but can be done. 25mg is a perfect recreational dose, at least for me.

Not clear what you mean by "generic."  As the prior post points out, there are no real "generics" for ED drugs.

I have heard that with a legitimate prescription, you can buy from Canadian pharmacies at a substantial discount, but have never done it.

You can also purchase generic versions of all ED meds from overseas sources, particularly India, where US patent laws either do not apply or are not enforced.  Some people say to stay away from these sources as the quality may be bad; others swear by them.   Search the General Board and, I believe, the Over 60 Board, and you will find discussions, sources and recommendations.

I did the pistachio nut regimen as suggested by the provided link. It worked fine but eventually had to have surgery for carpel tunnel. Opening all those nuts wrecked havoc on the fingers and wrists.
Not to speak of the significant lost time for my masturbation schedule.
I have found the generics to be highly effective for ED. However, quality varies as controls in
manufacturing differ. Most are produced in India and a secondary market is emerging in the UK.
Costs are all over the board, from roughly .60 cents (my source for 200 at a pop), to $4.00 each.
Also, waiting for your shipment can seem like a lifetime if you don't plan ahead-up to 4 weeks
with some sites. Lastly, my take on this is that the generic's work better than the real stuff. Probably due to workers forgetting how much shit they've mixed up in the big drums, so Habib will throw another 6 gallons of Sildenafil in the tub and keep-on-a-stirring.
And remember, the most common side effects of VIAGRA are headache, facial flushing, and upset stomach. Less commonly, bluish vision, blurred vision, or sensitivity to light may briefly occur.  
My massage therapist is writing this for me cuz I'm fuckin blind.