You could try making your own. This recipe works pretty well for me (I don't have time to pretreat most things either, though I do try to get baby poop out of the clothes before I wash!). It takes about 10 minutes to make this soap, and will last quite a while. And the ingredients for it cost me $7 (and considering that you can make umpteen batches with the powder and 3 with the bar, that's about as cheap as it gets!)
1/2 cup Washing Soda (Arm & Hammer, NOT Baking Soda)
1/2 cup Borax (20 Mule Team)
1/3 bar Fels Naptha Soap (Zote is good, too.) (grated)
[Note: I just made this with a 1/2 bar of Ivory soap. It seems to work just fine, and I figure it since Ivory soap has been my secret weapon against pretreating stains, it should work great for everything. The diapers I washed this morning came out looking as clean as can be!)
• In a large pot, heat 3 pints of water. Add the grated bar soap and stir until melted.
Then add the washing soda and borax. Stir until powder is dissolved, then remove from heat.
• In a 2 gallon clean pail, pour 1 quart of hot water and add the heated soap mixture.
Top pail with cold water and stir well.
• Let it sit, covered, for 24 hours before use.
• Use 1/2 cup per load, stirring soap before each use (will gel, somewhat).
• The 2-gallons will do appx. 64 loads of wash. Here are some hints:
Soap will be lumpy, goopy and gel-like. This is normal. Just give it a good stir before each and every use. Make sure soap is covered with a lid when not in use. You could also pour the homemade soap in old (and cleaned) laundry detergent bottles and shake well before each use.
For scented detergent, you can add between 10 to 15 drops of essential oil (per 2 gallons) to your homemade laundry detergent. Add once the soap has cooled to room temperature. Stir well and cover.