did you try the FASTA3 search at the EBI http://www.ebi.ac.uk ?
>My problem is, when I enter my sequence of interest (102 nt) in BLASTn,
>it returns only short, high identity sequences (ie, 15 bp, 95%
>identity). Even by significantly increasing my expect value and
>allowing a large number of hits, BLAST won't return long sequences
>unless they have very high sequence identity.