The cheapest option is a hipster PDA. Get a pen and some note paper that fits in your wallet. Use that for ubiquitous capture. It is also easy to write down errands and other things you do in the Moving / Walking / At Gym / In Car or whichever context. Setting up a Pocket Mod Report, is a very good idea that fits into this model.
David Allen sells a less than cheap wallet for this.
I personally used a small collection of card stock sticky notes back to back
3M Post-it Cards MMM634RVB Ruled, Restickable, 3"x4", White, 50 Per Pack Cat 634RV
3M Post-It Padded Cards 634-YBG Yellow Blue Green Restickable
Even with an Android phone, I still use these cards for a portion of my capture. As fast as the phone is, I can open my wallet and write a note on the cards without breaking eye contact.
Hipster PDA, is a similar idea, using small cards and clip
en.wikipedia.org/wiki/Hipster_PDA
Since getting an Android phone, I've decided to fragment my system for those moving context above. I'm using Mobisle Notes. There are even context aware apps like List Plus that could be set to alert you, when you are near the dry cleaner, by the GPS. However, I cannot say I yet trust any App enough. The paper solution worked perfectly for me. It took a week or two to develop the habit of looking at the list every time before leaving one context, but after that it was perfect (other than having to also check it as done in TR and cross it off the card list).
The real solution would be a TR Android App.