Can't find a deal to save my life Portland, OR - Tokyo, Japan - HELP!

[BigHurt]

I've been looking everyone online and I just can't find a great deal (imo) for a roundtrip flight from Portland, OR (PDX) to Tokyo, Japan (TYO). Dates are fairly flexible:

Depart: Last week in April, 27th - 30th
Arrive: First week in May, 4th - 7th
Cost: < $750 including taxes

If you know of a good site dealing with international flights to Japan, let me know!

Also, for those who frequently travel internationally, when are the sweet spots to order your tickets? Am I too early, or too late?

Thanks for responses!

[BigHurt]

bump... :)

[LockStock]

<$750 is pretty unlikely. I found Delta for $860 4/27-5/4.

[spendandsave]

$808 through NorthWest for 4/27 - 5/6. Nonstop as well.