Fiberglass arrows are a little heavier than wooden arrows but they can be made straighter which will give you more consistency. The trade off is that you lose a little speed.  Some people don't like them as they can be brittle but you can also get very good results with them.

Here are some great fibreglass arrows on ebay right now

12 Shiny Black Fiberglass Target Practice Arrows 28 $35.50 Time Remaining: 22d 6h 59m Buy It Now : $35.50

New 3pc Pack of 26 Fiberglass Arrow for Compound Bow $10.49 Time Remaining: 10h 30m Buy It Now : $11.99

12 Shiny Black Fiberglass Target Practice Arrows 26 $32.50 Time Remaining: 21d 12h 11m Buy It Now : $32.50

12 Shiny Black Fiberglass Target Practice Arrows 307 $34.90 Time Remaining: 4d 15h 57m Buy It Now : $34.90

ARROWS 1 DOZEN FIBERGLASS TARGET ARROWS $28.95 Time Remaining: 4d 21h 46m Buy It Now : $28.95

12 Shiny Black Fiberglass Target Practice Arrows 22 $29.50 Time Remaining: 24d 13h 28m Buy It Now : $29.50

9 MicroFlite Fiberglass Arrow Aluminum Point Inserts $6.99 Time Remaining: 29d 2h 5m Buy It Now : $6.99

10 MicroFlite Fiberglass Arrow Aluminum Nock Inserts $6.99 Time Remaining: 27d 11h 19m Buy It Now : $6.99

3 x Compound 30 Archery Bow Fiberglass Arrows for Long Recurve Bows $12.99 Time Remaining: 9d 7h 28m Buy It Now : $12.99