Biking backpack rec's

I am teacher with less than a week left before summer break. I coach swimming in the summer and usually ride the 20 miles each way to practice about 3-4 times a week. I would like to use some of these rides as harder efforts but I am struggling with how to carry my gear. Last year I left some stuff at the pool, but will be unable to do that this year. I don’t need anything too big. Things I have to carry
-Sack Lunch and snacks
-Tshirt
-Shorts
-Goggles
-sandals
-random papers (for workouts etc) - figure a clipboard size

I’d like something that would stay on for harder type efforts. I’ll also ride my tri bike at least once a week so it would need to be able to stay on in the aero bars.

Thanks in advance,
Lee

I like the Osprey Talon series for lightweight packs. They come in a variety of sizes.

From the web site:

Designed for the fast, adventure oriented enthusiast, the Talon Series offers a unique melding of torso adjustability in an active, lightweight pack.

1 – AirScape backpanel with ridge molded foam and air channels
2 – Torso adjustable harness (sewn-in on 11)
3 – Mesh covered perforated harness with stretch energy gel pockets
4 – Elastic stretch sternum strap
5 – Mesh covered perforated hipbelt with zippered stretch mesh pockets (mesh hipbelt on 11)
6 – Easy access hydration compartment

Deuter Cross-air - has an elevated mesh back so your back wont get blazing hot. I ride 30 miles hard effort each way to work with my work clothes in the bag & its perfect. on sale at REI.com here: http://www.rei.com/REI-Outlet/product/751718


It has a hydration bladder but I just took it out. No problem fitting size 13 mens shoes, pants, dress shirt, undershirt belt plus my lunch. I’ve also carried a laptop in it but it was a bit heavy.