The problem is these devices are not available in local market and getting them from farnell or RS will take atleast 3 weeks I need to implement this isolated RS232 <-> TTL converter urgently.
In such a situation, I realy can not think of any suggestion other that have a look at the appnote I suggested (pseudo isolated) and see if you can extract sonething there to combine with Ijaszs suggestions.

The problem with the 2 links you show is that neither has true RS232 on "the other side". The Asim Khan version is not adhering to the standard on either side thus, I assume you will run into the same problems as the "you do not need MAX232(equivalent)" to interface with a PC "suggestions".
Ijaszs suggestion should be possible if on the uC board where "logic level" Rx and Tx is required(RS232 <-> TTL converter). I am, however a bit weary of powering a 232 chip from the lines, it may work with some PCs and not with others since even PC manufacturers "cheat" on the 232 specs.
Is it, at all possible, that you use a small isolated switcher to power the PC side.

If you would state why you need isolated RS232, there may be other possibilities than isolated. Also, is this bidirectional or only one direction?

Is this a one-off (installation #3 keep blowing the chips) or a more general solution?

Erik