Do a search on the forums for weighted balls. Believe me when I say this, " there is an ongoing debate on this one it works for some and it doesn't work for others. ".
IF you have bad mechanics do not even attempt to try these things. IF you have good mechanics look into it and if at all possible video tape yourself!!!!
As far as cords are concerned, you can get tubing pretty much anywhere but I'd recommend a good site, and of course I have no affliation with this person for the record, which is
http://www.jaegersports.com. The resistance bands are a gem and I have been on the program as well as my son for about a year or so. Great exercises and good arm care go a long way.