convert int to bytea

Hi all,

I'm trying to write a trigger that converts integer to bytea.
My schema is like this:

Create table xx (
id int,
....
...
data bytea);

the first 3 bytes of data are the binary representation of id
(id  is extracted from data by  the application)

I can occur that id change in that case data has to change too!

select 124::bytea doesn't work

Is there an other way? (preferabily simple :)

Regards
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